function readmud_sp, FilePath, FromSecond, ToSecond, sample_rate, station_id

if station_id eq 'MCM' then num_channels = 2
if station_id eq 'SPA' then num_channels = 3

; open the MUD file:
dat_fh = 1
openr, dat_fh, filepath, /get_lun

; read header
FileFlag = bytarr(4)
NumChannels = 0
SampleRate = 0
SampleSize = 0
StartYear = 0
StartMonth = 0
StartDay = 0
StationName = bytarr(4)
NumSeconds = long(0)
Reserved1 = long(0)
Reserved2 = long(0)

readu, dat_fh, FileFlag
readu, dat_fh, NumChannels
readu, dat_fh, SampleRate
readu, dat_fh, SampleSize
readu, dat_fh, StartYear
readu, dat_fh, StartMonth
readu, dat_fh, StartDay
readu, dat_fh, StationName
readu, dat_fh, NumSeconds
readu, dat_fh, Reserved1
readu, dat_fh, Reserved2

; set sample buffer size
SampleBufferSize = SampleRate * SampleSize / 8

; allocate data array
if num_channels eq 2 then $
   Data_Array = fltarr(2, (long(ToSecond)-long(FromSecond)) * sample_rate)
if num_channels eq 3 then $
   Data_Array = fltarr(3, (long(ToSecond)-long(FromSecond)) * sample_rate)

; allocate temp buffer
if num_channels eq 2 then Buffer_Array = fltarr(10, 2)
if num_channels eq 3 then Buffer_Array = fltarr(10, 3)

; move to the 1st data position
Offset = long(32)
Offset = Offset + FromSecond * (4 + SampleBufferSize * NumChannels)
POINT_LUN, dat_fh, Offset

; read samples
Second = long(0)
FOR n = long(0), long(ToSecond)-long(FromSecond)-1 DO BEGIN
    readu, dat_fh, Second

    ; read 10-sample chunk of 2 channels
    readu, dat_fh, Buffer_Array

    ; assign the samples to the data array
    FOR m = 0, 9 DO BEGIN
        Data_Array(0, n * 10 + m) = Buffer_Array(m, 0)
        Data_Array(1, n * 10 + m) = Buffer_Array(m, 1)
        if num_channels eq 3 then begin
           Data_Array(2, n * 10 + m) = Buffer_Array(m, 2)
        endif
    ENDFOR
ENDFOR

; close the file
free_lun, dat_fh

return, Data_Array
end